I just installed a Volvo R-134 retrofit kit in my 1991 240. All went well thanks to this board and Volvo service bulletin. I blew out high and low pressure hoses and lines, evaperator and condenser. I dumped the old oil and added ester oil to compressor. I added 11oz. can R-134 and low-side pressure was 25psi. I added another 11oz. and low-side pressure was 65psi at idle. The reading fluctuates according to engine speed. At high idle it was 25psi. The directions warn 65psi is dangerously high. I'm not getting much cold air yet and Volvo says my target fill is 2.2lbs R-134.

Should I ignore the low-side psi and continue to add R-134, or is something wrong? I have no way to check high-side pressure. Thank you in advance. JDL
P.S. Each 11oz. can took about 30 min. to empty. I thought the system just sucked it up.????

With the newer systems, you CAN'T measure pressure-side readings anyway, so don't be forced into thinking that there is no other way. Even professional A/C techs can't service Volvo A/C with any other readings than the low side pressure, on newer factory-fill R134 systems. You just have to charge EXACTLY the recommended amount into the system to know that you have the right amount.

You have to consider a few things.

One, you changed the fixed orifice with a brand new one straight from the Volvo kit. If you didn't your conversion is going to stink.

Two. The low pressure reading is obviously high, but sounds as if it got better along the way. That's a good sign. I don't think that 22oz is enough.

To get better (faster) charging, you can always run a garden hose over the condenser and raise the idle speed. If you are trying to charge, you're looking for LOW suction pressure. You can achieve low suction pressure by hosing the condenser and turning the inside air to floor setting, fan position II. If you get the low side too high, you'll find that it won't take refrigerant.

Also, the high low pressure readings might be a result of leftover air in the system from not vacumming it out before charging. You should ideally vacuum out the system to get the moisture out.

One thing that will/does help your conversion, is to look for the high pressure fan switch on the high pressure line, along the right side frame rail in the engine compartment. It's somewhere in the vicinity of the alternator forward, but it's a little "J" that comes off of the high side pipe. Take the wiring harness OFF of that switch, put a wire between the two terminals of the wiring harness, tape it all off, and now the condenser fan will run whenever the system is on. That becomes a big help later on.

Try getting the remainder of the charge into the system, but if anything, err on the low side. You'll otherwise see too much system cycling from the A/C. You might want to set the pressure switch to about 22lbs if not even 20-21. That keeps the evaporator cooler, and means more cool air from you. It prevents the system from cycling out at higher temp/pressure. That is a very good way to drop the output of the system significantly. You should see temps in the high 30s during the day.

Believe it or not, one other coolness factor, is to coat the dashboard with STP Son of a Gun protectant (or the protectant of your choice). The gloss will reflect on the windshield, but it'll keep a LOT of heat out of the cabin. Vent temps won't change, but the interior temp will change for the better.
--
1992 940 wagon, 72k

Chris, thank you for the tip on jumping the condenser fan. I'll do it when I get things working.

Here is the whole sad story. I now have 32oz. of r-134 in the system, which is about 3oz. shy of a complete fill. The low-side pressure is between 25 - 40 psi. There is no cooling at all.

The small metal line from the evaporator to the condenser (the one that has the expansion valve) is ice cold to a point where it is dripping condensate all over the place. The metal line & large hose from the condenser to the compressor is very hot and the big hose from the compressor to the rec/drier is medium.

Here are some things I may have done wrong during the refit:
1) Blew out the condenser with 75lbs compressed air (not sure which direction)
2) Blew out the evaporator with 75lbs air
3) blew out the compressor with 75lbs air(although there wasn't a tight seal, so most of the air just came right back out)
4) I noticed that the old expansion valve was in it's pipe where the tab you grab to pull it out was flush with the end of the pipe. It came out intact and clean. When I installed the new one I couldn't get it in that far, so the tab (1/2 inch)was extending out from the pipe, but the valve felt snug and since the female part of that fitting is bell shaped, the tab fit inside.

If anyone has a clue what I did wrong and could explain how to fix it I'd appreciate it. JDL

Are you reading the pressure gauge with the can attached and open? If so the can pressure is misleading you into thinking it is the system pressure. It just sounds like what you see with the can open to the pressure gauge. Also, are you sure you have the hoses in the correct orientatuion to depress and schrader valves that are in line?

I'm taking the psi with guage only. The situation has changed a little. I drove the car around for an hour with AC on. At amb.80 temp, AC was blowing 53. I rechecked low-side pressure and now it's at 25psi w/compressor engaged, 40psi unengaged at idle. It only has 22oz R-134 so far.

About the schrader valves --- I'm not familiar with them, but I can tell you that all hoses and lines are replaced as they were, and I didn't notice anything strange. Which lines are they in and what do they do? JDL

A schrader valve is what keeps the air in your tires. Push the little pin in the center and the air can go in or out. Which way depends on relative pressure.

The fittings on the a/c compressor - R12 type - have similar Schrader valves on both high and low side. If a line is connected to a fitting incorrectly such that the Schrader valve isn't open, refrigerant flows slowly or not at all.

Remember that a can is not a pound. It's easy to mis-calculate how much is needed. The fender tag on the Left side should give the amount of R12 needed, RS134a usually is 85% of that. Mine wants 48 ounces R12, so I'll use 40 ounces of RS134a.

Good Luck,

Bob

:>)

You need to connect the high side of your charging manifold to
the compressor discharge and the low side to your compressor
suction and measure BOTH pressures.

Did you evacuate to get all the air out of your system?
--
George Downs Bartlesville, Oklahoma